Motor system employing analog encoded hall effect sensor position information for reduced wiring

Abstract

A system has a sensor assembly mounted adjacent to a moving magnetic member such as a motor rotor to sense its position. The sensor assembly includes Hall-effect sensors each having a binary output, configured such that distinct positions of the moving magnetic member correspond to distinct digital patterns of the outputs of the Hall-effect sensors. Encoding circuitry is coupled to the outputs of the Hall-effect sensors to generate a multi-valued analog output, distinct values of the multi-valued analog output representing corresponding distinct digital patterns of the outputs of the Hall-effect sensors. The encoding circuitry may employ a ladder network with weighted-value resistors contributing different components of an analog current sensed by the controller. The sensed current can be converted to digital position information using suitable analog-to-digital conversion circuitry. The multi-valued analog output can be conveyed on a single wire in contrast to the prior art which requires one wire per Hall-effect sensor.

1. Apparatus, comprising:
 a moving magnetic member; and 
 a sensor assembly mounted immediately adjacent to the moving magnetic member to sense the position thereof, the sensor assembly including:
 a plurality of Hall-effect sensors each having a binary output, the Hall-effect sensors being configured such that distinct positions of the moving magnetic member correspond to distinct digital patterns of the set of outputs of the Hall-effect sensors; and 
 encoding circuitry coupled to the outputs of the Hall-effect sensors, the encoding circuitry being operative to generate a multi-valued analog output of the sensor assembly, each distinct value of the multi-valued analog output representing a corresponding one of the distinct digital patterns of the set of outputs of the Hall-effect sensors. 
 
 
     
     
       2. Apparatus according to  claim 1  wherein the multi-valued analog output of the sensor assembly comprises a current output, and wherein the encoding circuitry comprises a ladder network having ladder sections each coupled to a respective one of the Hall-effect sensors, the ladder sections including respective weighting resistors operative to establish respective components of the current output of the sensor assembly. 
     
     
       3. Apparatus according to  claim 1  wherein the encoding circuitry comprises a plurality of transistor amplifiers having respective inputs coupled to respective ones of the Hall-effect sensors and having respective outputs coupled together to generate the multi-valued analog output of the sensor assembly. 
     
     
       4. Apparatus according to  claim 1  wherein the moving magnetic member comprises a rotor of an electric motor, and wherein the Hall-effect sensors of the sensor assembly are configured such that the distinct digital patterns of the set of outputs of the Hall-effect sensors correspond to distinct rotational positions of the moving magnetic member. 
     
     
       5. Apparatus according to  claim 4  wherein the electric motor has a diameter of less than approximately one-half inch. 
     
     
       6. Apparatus according to  claim 1  further comprising a wiring harness providing the coupling between the sensor assembly and the controller, the wiring harness including first and second wires carrying supply current and a third wire carrying the multi-valued analog output of the sensor assembly. 
     
     
       7. Apparatus according to  claim 1  wherein the sensor assembly comprises a circuit board on which the Hall-effect sensors and the encoding circuitry are mounted. 
     
     
       8. Apparatus, comprising:
 the apparatus of  claim 1 ; and 
 a controller coupled to receive the analog output of the sensor assembly and to utilize the position information provided by the distinct values of the analog output to control the operation of the moving magnetic member. 
 
     
     
       9. Apparatus according to  claim 8  wherein:
 the multi-valued analog output of the sensor assembly comprises a current output; 
 the encoding circuitry comprises a resistor ladder network having ladder sections each coupled to a respective one of the Hall-effect sensors, the ladder sections including respective weighting resistors operative to establish respective components of the current output of the sensor assembly; and 
 the controller includes:
 a sense resistor coupled to the resistor ladder network to develop an analog voltage corresponding to the current output of the sensor assembly; and 
 conversion circuitry operative to convert the analog voltage into a corresponding digital value used by digital control circuitry of the controller to control the operation of the moving magnetic member. 
 
 
     
     
       10. Apparatus according to  claim 1 , wherein the moving magnetic member comprises a rotor of an electric motor, and wherein the sensor assembly includes a disk-shaped circuit board on which the Hall-effect sensors and the encoding circuitry are disposed, the disk-shaped circuit board being disposed at one end of the electric motor and having a center portion in which the encoding circuitry is located and about which the Hall-effect sensors are symmetrically arranged. 
     
     
       11. Apparatus according to  claim 10 , wherein the disk-shaped circuit board further includes a connector for coupling to a wiring harness providing connections between the disk-shaped circuit board and a controller, the connections including one connection for carrying the multi-valued analog output to the controller, the connector being located between a pair of the Hall-effect sensors. 
     
     
       12. Apparatus according to  claim 11 , wherein the connector includes a set of only three terminations for three wires of the wiring harness, the three terminations including two terminations for receiving power from the controller and a third termination for providing the multi-valued analog signal to the controller. 
     
     
       13. Apparatus, comprising:
 a moving magnetic member; and 
 a sensor assembly mounted immediately adjacent to the moving magnetic member to sense the position thereof, the sensor assembly including:
 a plurality of Hall-effect sensors each having a binary output, the Hall-effect sensors being configured such that distinct positions of the moving magnetic member correspond to distinct digital patterns of the set of outputs of the Hall-effect sensors; and 
 encoding circuitry coupled to the outputs of the Hall-effect sensors, the encoding circuitry being operative to generate a multi-valued analog output of the sensor assembly, each distinct value of the multi-valued analog output representing a corresponding one of the distinct digital patterns of the set of outputs of the Hall-effect sensors, 
 
 wherein the multi-valued analog output of the sensor assembly comprises a current output, and wherein the encoding circuitry comprises a ladder network having ladder sections each coupled to a respective one of the Hall-effect sensors, the ladder sections including respective weighting resistors operative to establish respective components of the current output of the sensor assembly. 
 
     
     
       14. Apparatus according to  claim 13  wherein the encoding circuitry comprises a plurality of transistor amplifiers having respective inputs coupled to respective ones of the Hall-effect sensors and having respective outputs coupled together to generate the multi-valued analog output of the sensor assembly. 
     
     
       15. Apparatus, comprising:
 the apparatus of  claim 13 ; and 
 a controller coupled to receive the analog output of the sensor assembly and to utilize the position information provided by the distinct values of the analog output to control the operation of the moving magnetic member. 
 
     
     
       16. Apparatus according to  claim 15  wherein the controller includes:
 a sense resistor coupled to the resistor ladder network to develop an analog voltage corresponding to the current output of the sensor assembly; and 
 conversion circuitry operative to convert the analog voltage into a corresponding digital value used by digital control circuitry of the controller to control the operation of the moving magnetic member.